Sheet-like components, such as for example membranes, in particular membrane electrode assemblies, or MEAs for short, for fuel cells, are predominantly produced in continuous production processes, for example in the form of roll product, or are produced continuously by coating or plane-parallel lamination of a plurality of webs of material to one another, these webs of material themselves at least in some cases also being in the form of roll product.
In particular in the case of MEAs, it is necessary to test for perforations, in order to be able to ensure that the fuel cells which are subsequently produced therefrom will operate reliably. In this context, there are difficulties in integrating a test of this type in the continuous production process. The integration of the testing of components of this type in manufacture requires a short test time and a high reliability of the test.
A test method which is known from DE 697 04 571 T2 is based on the detection of an exothermic chemical reaction at the perforations in an MEA. To carry out the test method, this publication provides a test apparatus having two gas spaces, which can be supplied with different gases that are able to react exothermically with one another, the gas spaces being separated from one another by the MEA, which can be clamped areally between the gas spaces. After air and/or other residual gas has been displaced out of the gas spaces by means of an inert gas, the two gas spaces are filled with different gases, with the gas in one gas space being at a greater pressure than the gas in the other gas space. The gas which is under a greater pressure penetrates through the MEA at the perforations and reacts exothermically with the other gas in the presence of a catalyst. The heat which is generated is detected by means of a thermal imaging camera.
One drawback of this method is the relatively long measurement period of typically a few minutes, associated with the need to purge the gas spaces, the complicated structure of the test apparatus, which presupposes the presence of a catalyst, and the potential danger of simultaneously handling gases which react with one another, which is associated with the risk of spontaneous combustion of the membrane and therefore of sudden, complete contact between the two gases, with the possible consequence of an explosion in the case of gases which react hypergollically with one another. Furthermore, these dangers may also occur if the test apparatus is not handled correctly, for example if an excessively high pressure is set on one side of the membrane, with the result that the membrane bursts. If only small quantities of gas penetrate through the MEA at the perforations, it is also the case that only small amounts of heat will be generated, which leads to error sources on account of the low temperature differences, for example caused by the body heat of people who are present.